Perf/uniform solver

[THinnerichs]

Draft PR to fix type instabilities in HerbConstraints.
The root cause is the UniformIterator not knowing what subtype of AbstractRuleNode it faces. However, these are only StateHole or RuleNode.

We now transform every RuleNode to a StateHole first, and then only handle this case.

TODO:

• StateHole(..., ::Rulenode) does not know the domain size, which hence has to be passed. Let us find a cleaner solution to this.

[codecov]

Codecov Report

❌ Patch coverage is 94.11765% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.23%. Comparing base (7e229a0) to head (fa11b8d).
⚠️ Report is 65 commits behind head on master.

Files with missing lines	Patch %	Lines
src/solver/uniform_solver/uniform_solver.jl	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #77      +/-   ##
==========================================
+ Coverage   77.06%   77.23%   +0.16%     
==========================================
  Files          31       31              
  Lines        1395     1401       +6     
==========================================
+ Hits         1075     1082       +7     
+ Misses        320      319       -1     

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